Telephone-exchange system.



L.H.JOHNS'ON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 10. 1915.

Patented Jan. 2, 1917.

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L. H. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. I0. 1915. 1,210,652. Patented Jan. 2,1917.

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TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAR. 10.1915.

Patented Jan. 2, 1917.

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W/ln e55 es LEWIS H. JOHNSON,

MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED,

NEW YORK.

OF BLOOMFIELD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- A CORPORATION OF TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Jan. 2, 1917.

Application filed March 10, 1915. Serial No. 13,460.

change systems, and more particularly to such systems of the divided multiple type for use in interconnecting subscribers whose telephone lines terminate in different central offices.

The object of this invention is the pro vision of such a system whereby during hours of light load it is possible to dispense with the services of all operators at the I operation of the system shown in the drawtrunk boards.

In accordance with one feature of this in-' vention, a transfer circuit is provided be-: tween a trunk board and a subscribers bogj rd' o a distant central office during hours of light load being connected with one end of the transfer circuit. At the subscribers board there is provided in the at a central oflice, the incoming end trunk circuit from a transfer circuit a signal which is under the control of the distant central office.

In accordance with another feature of this invention, there is associated with the cir-i cuits of such a system signal control apparatus by means of which complete supervision over a connection between two subscribers, whose telephone lines terminate at different central offices, is given to the operator at the originating central office.

This invention will be more fully understood by reference to the drawings showing one embodiment of the invention, in which all apparatus is shown in its normal and unactuated condition, and wherein.

Figure 1 shows a subscribers line terminating at a central office, and link conductors and the outgoing end of a trunk circuit at the central office; Fig. Qshows the incoming end of the trunk "circuit of Fig. 1 terminating at a trunk board at a second central office, a transfer circuit thereat for extending the trunk circuit to a subscribers board at this second central office, and the answering end of link conductors thereat; and Fig. 3 shows link conductors at the second central office and a subscribersline terminating thereat.

Inthe drawings there are shown subscribers stations A and B, the lines from which terminate at central offices C and D respectively. A cord circuit E at the central office C is adapted to connect subscribers station A with a trunk circuit F extending between a switchboard at the central office C to a trunk board at central office D. A transfer circuit Gr extends from the trunk board to a subscribers board at the central office D and is adapted to connect the incoming end of the trunk circuit F with the answering end of a cord circuit H at the subscribers board of the central office D, the calling end of the cord circuit H connecting with the line of subscriber B.

1 It is believed that this invention will be fully understood from a description of the ings, and it will be so described.

Assuming that the period of light load in a central office is commencing, the plug of the trunk circuit F is inserted into jack 5 of the transfer circuit G, whereupon the trunk circuit F is'extended from the trunk board to the subscribers board of central office D. Thereafter the operator at the subscribers board handles all connections wherein trunk circuit F is involved in the same manner as the operator at the trunk board would handle such connections were the trunk circuit not connected to the transfer circuit. It will be observed that when the trunk circuit F was connected to the transfer circuit G, all

apparatus associated with both circuits remained in its normal and unactuated condition.

1 It will now be assumed that subscriber A desiresto converse with subscriber B, and it will be furthermore assumed that A has signaled central office C and that the operator at C has answered and has been informed that the wanted line is that of subscriber B terminating at another central office D. The operator at C now communicates with the operator at D by means of a call wire circuit (not shown since such circuits are well understood and since it forms no part of this invention), advising the number of the wanted line and in turn is advised to use trunk circuit F for this particular connection. The operator at thereupon inserts the calling plug of cord circuit E into jack 6 of the trunk circuit F completing a circuit from the live pole of battery 7, through winding of supervisory relay 8, conductor 9, ring contacts 10 and,

11' of the plug and jack, conductor 12, winding 13 of'relay 14, conductor 15, tip con tacts 16 and 17 of jack and plug, conductor 18 to ground. Current in this path actuates relay .14, but since winding 13 thereof is of high resistance, relay 8' which is of low re sistance does not receive sufficient current to permit the operation thereof. When the above traced circuit was completed a second circuit was completed from battery 7, through conductor 20, supervisory signal 21, resistance 22, sleeve contacts 23 and 24 of plug and jack, and resistance 25 to ground, operating supervisory signal 21. When relay 14 was operated a circuit was completed from the live pole of battery 30, through resistance 31, windings 32 and 33 of relay 34, sleeve contacts 35 and 36 of the jack and plug, winding of relay 37, contact lay 14, contact 39 of relay 37 and resistance 40 to ground. Current in this path actuates relay 34, but since the combined resistance of resistance 31 and the windings 32 and 33 of relay 34 is high as compared to the resistance of thewinding of relay 37, relay 37 is not actuated. lVhen relay 14 was actuated a circuit for signal 41 was completed from battery 42 operating this signal. The actuation of relay 34 completed a circuit from the live pole of battery 45, through signal 46, contact 47 of'relay 48 and contact 49 of relay 34 to ground operating signal 46, The operatorat central office D observing signal 46 inserts the answering plug of cord circuit H into the jackof'the transfer cir cuit. Cr, completing a circuit from the live pole of battery 55, through contact 56 of relay 57,- contact 58 of relay 59, resistance 60,

winding of'relay 61, sleeve contacts 62 and 63 of answering plug andjack, and windings 64 and 65 of relay 48 to ground. Current in this path actuates relay 48, but since the resistance of relay 61 is low compared to that of the combine'd'resistaince of the windings of relay 48, relay 61 is not actuated. Relay 48 opens the circuit of signal 46 at contact 47 and by closure of its con tact 66 completes a circuit from battery 42, through sleeve contacts 36 ands35 ofthe plug and jack 5, winding 33 of relay 34 and contact 66 of relay 48 to ground. Current in this path is sufficient toractuate relay 37 which opens its contact 39 and closes its contacts 67 and68. The closure of contact 67 com pletes a circuit from battery 70 through winding ofrelay 71, contact 72 of relay 73,

contact '74 of relay 75, contact 67 of relay.

37 contact 38 of relay 14, winding of relay 37, sleeve contacts 36 and 35 of plug and jack 5 winding 33 of relay 34 and contact 66 of relay 48 to ground. Current in this path. actuates relay 71: which opens its con 38 of resignal 41, winding of relay 37,

"thereby, whereupon signal 41 is e'lfaced.

The closure of contact 79 of'relay"71"connects a source of ringing current 80 to the ring side 81 of the trunk circuit F, but since the ring side of the connected transfer circuit G and cord circuit H is open, the ringing current at this time performs no function.

The operator at D'after having inserted the answering plug in the jack of the trans-- fer circuit G, inserts the calling plug of the cord circuit H into the jack' of the line from substation B, completing a circuit from battery 85 through signal 86, resistance 87, sleeve contacts 88 and'89 of the plug and jack and winding of cut-off relay 90 to ground, operating signal 86 and cutofi' relay 90 disconnecting the limbs of the line from line relay 91. The operator at D now operates key 92 connecting a source of r1nging current to the called line. Signal 86 remains operated until subscriber Bremoves receiver from switchhook, and the operator may therefore continue to ring as long as signal 86 is operated. Upon removal of the receiver at subscriber B a circult is completed from battery 93, through winding of supervisory relay 94, contact 95 of relay 96, ring contacts 97 and '98 of plug and Jack, line of subscriber B, tip contacts 99 and 100 of jack and plug and contact 101 of relay 96 to ground. Current in this path actuates relay 94, completing a circuit from battery 93, through'contact 102 of relay '94, winding of relay 103, resistance 87, sleeve contacts 88 and 89, and winding of cutoff relay 90 to ground. Since the resistance of relay 1-03 is low, a low resistance'shunt is placed around signal 86, effacing said signal. -Current in completing a low resistance path for cur rent from the source'80. This path may be traced from the sour.ce-80,' th1';ough winding of relay 75, contact 7 9 tor 81, ring contacts1'04 and 105 of plug and jack 5, ring contacts 106 and 107 of jack and answering plug, contact 108 of relay 61, contact 1'O9'and winding of slow operating relay 57, contact 1100f relay 103, and contact 111 of relay 61 to ground. Sufficient current flowsthrough relay to operate it, whereupon the short circuit of relay 73 is removed, permitting relay 73 to operate and lock up over a circuit from battery-120, contact 121 of'relay 7 3,,contact 67 of relay 37, contact38 'of'relay 14, winding of relay 37 sleeve contacts 36 and 35 of the plug ancl'jack 5, winding 33 ofrelay 34 and contact 66 of relay 48 to ground. Current from battery 120 to the winding of relay 73 shunts relay 7 1, whereupon relay 71 releases completing the talking circuit-10f of relay 71, conduc-.

the trunk circuit F. Relay 57 was included in the above traced path from source 80 and was actuated opening its contacts 56 and 109 and closing contacts 122 and 123. The 010s ing of contact 122 completes a circuit from battery 124, through the winding of relay 96, contact 122 and winding of relay 57, contact 110 of relay 103 and contact 111 of relay 61 to ground. The closure of contact 123 completes a circuit from battery 55, thorugh contact 123 of relay 57, contact 125 and winding of relay 103, resistance 87, sleeve contacts 88 and 89 of the calling plug and jack and winding 90 to ground. The opening of contact 56 removes the shunt from relay 59, whereupon relay 59 is operated over a circuit from battery 126, through the winding of relay 59, resistance 60, winding of relay 61, sleeve contacts 62 and 63 of the answering plug and jack, and windings 64 and 65 of relay 48 to ground. Relay 59 in operating opens contact 58 and closes contact 127 thereby shunting the resistance 60, whereby: the same resistance of the sleeve circuit is maintained. Current in the path including relay 96 operates this relay, which opens its contacts 95 and 101 and closes contacts 128 and 129, the opening of the first mentioned contacts removes the repeating coil 130 and the supervisory relay 94 from the circuit, while the closure of the contacts 128 and 129 completes a circuit from battery 140 through the winding of supervisory relay 141, contact 77 of relay 71, ring contacts 104 and 105 of plug and jack 5, ring conductor 142 of the transfer circuit G, ring contacts 106 and 107 of jack and answering plug, contact 108 of relay 61, conductor 143, contact 128 of relay 96, ring contacts 97 and 98 of calling plug and jack, line or subscriber B, tip contacts 99 and 100 of jack and calling plug, contact 129 of relay 96, conductor 144, contact 145 of relay 61, tip contacts 146 and 147 of answering plug and jack, tip conductor 148 of the transfer circuit G, tip contacts 149 and 150 of jack 5 and plug, contact 68 of relay 37, and contact 76 of relay 71 to ground. Current in this path actuates supervisory relay 141 completing a path at contact 151 of relay 141 for current from battery 7, through low resistance winding 152 of relay 14, shunting the high-resistance winding 13 thereof and permitting sufiicient current to flow through the winding of supervisory relay 8 to operate this relay. The operation of relay 8 completes at its contact 153 a path through low resistance 154 shunting signal 21 thereby efiacing said signal.

lVhen the connected subscribers have completed the conversation, the receivers are restored to the switchhooks. Restoration of receiver by A permits supervisory signal 155 to operate to give a disconnect signal. Restoration of receiver by B opens the circuit of supervisory relay 141 of the trunk circuit F, which releases, opening the circuit of the low resistance winding 152 of relay 14. Supervisory relay 8 in the cord circuit E thereupon receives less current, causing this relay to release and permit the operation of supervisory signal 21 to furnish a disconnect signal. The operator at central ofiice O upon observing the disconnect signals 21 and 155 removes the answering and calling plugs from the jacks. The removal of the answering plug restores to normal condition the apparatus associated therewith and the line apparatus, while the removal of the calling plug restores to normal the cord circuit apparatus associated therewith and opensthe circuit of winding 13 of relay 14. Relay 14 thereupon releases, opening the circuit of relay 73, and permits the establishing of the following circuits: 1) From battery 42, signal 41, winding of relay 37, sleeve contacts 36 and 35 of the plug and jack 5, winding 33 of relay 34 and contact 66 of relay 48 to ground. (2) From battery 30, through resistance 31, winding 32 of relay 34, contact 66 of relay 48 to ground. The flow of current through the two windings of relay 34 in the direction mentioned renders the windings differential in action, whereupon relay 34 releases, opening contact 49 and closing contact 156. The closure of contact 156 completes a short circuit for the high resistance winding 65 of relay 48, thereby permitting sufiicient current to flow through the winding of relay 61 to operate this relay. The operation of relay 61 opens contact 111, whereupon relays 96 and 57 release, and relay 57 in releasing opens the circuit of relay 103 which releases. The operation of relay 61 also closes contact 157 completing a circuit for supervisory signal 158, which operates to furnish a disconnect signal. The release of relay 57 removes the shunt from supervisory signal 86, which thereupon operates to furnish a disconnect signal. The operator at central ofiice D observing disconnect signals 86 and 158, withdraws the answering and calling plugs from the jacks, permitting all apparatus to return to normal and unactuated condition.

It will be noted that by the utilization of the present invention, operators at the trunk boards may be eliminated during hours of light load; also the usual repeating coil of the cord circuit at the central oflice is eliminated from the completed talking circuit between two connected subscribers. Furthermore the operator at the originating central ofiice has complete supervision over an established connection, and the operator at the second central oiiice perform the usual duties of a trunk board operator in handling a trunked call.

It is also to be noted that the cord circuit H at central oflice D is arranged to function as an ordinary cord circuit in handling local calls. When the answering end of this cord circuit H is plugged into the jack of a subsfcribers line, marginal relay 61 operates connecting the repeating coil 130 in the circuit. In such a case relays 9 1, 103 and 160 control the supervisory signals 86 and 158. Also when relay 61 operates, relays 57, 59 and 96 are removed from the circuit and perform no function on a local call.

What is claimed is:

1. A telephone exchange system comprising a trunk circuit extending from one switchboard section to a second section, a transfer circuit connected to and extending the trunk circuit to a third section, a link circuit at the first section, a signaling device for the transfer circuit located at the third section, and a relay in the trunk circuit re sponsive to the connection of the link circuit therewith for causing the operation of the signaling device.

2. A telephone exchange system comprising subscribers lines terminating at a central office, a link circuit thereat, trunk and subscribers boards at a second central office, a trunk circuit oining said first central office and said trunk board, a transfer circuit connected to and extending said trunk circuit tosaid subscribers board, a signal for said transfer circuit at said subscribers board, and apparatus in said trunk circuit actuated upon connection of said link circuit therewith for causing the operation of said signal.

3. A telephone exchangesystem comprising subscribers lines terminating at a central oflice, a link circuit thereat, trunk and subscribers boards at a second central ofiice, a trunk circuit joining said first central office and said trunk board, a transfer circuit ccnnected'to and extending said trunk circuit to said subscribers board, a signal for said transfer circuit at said subscribers board, a control relay'for said signal nor mally unactuated when said trunk circuit is connected to said transfer circuit, and a relay associated with said trunk circuit c0ntrolling the actuation of said control relay and responsive to the connection of said link circuit with said trunk circuit to cause the operation of said signal.

4. A telephone exchange system comprising subscribers lines terminating at a central oflice, a link circuit thereat, trunk and subscribers boards at a second central oflice,

a trunk circuit joining said first central oflice and said trunk board, a transfer circuit connected to and extending said trunk circuit to said subscribers board, a signal for said transfer circuit at said subscribers board, a relay associated with said'trunk circuit responsive to the connection of said link circuit therewith to cause the operation of said signal, a link circuit at said subscribers board, and a relay associated with said transfer circuit and responsive to the connection of said second 'linkcircuit therewith torender said signal inoperative.

5. A telephone exchange system comprising a telephone line terminating at a central ofiice, trunk and subscribers boards at a second central oflice, a transfer circuit joining said boards, a trunk circuit joining said first central oiiice with said trunk board and connected to said transfer circuit, a link circuit connecting said telephone line with said trunk circuit, a telephone line terminating at said subscribers board a link circuit thereatconnecting said transfer circuit with said second telephone line, disconnect signals for aid first link circuit operated upon restoration of the receivers at the connected substations, and disconnect signals for said second link circuit operated when said first link circuit is disconnected from said trunk circuit.

6. A telephone exchange system comprising subscribers lines terminating at a cental oflice, a link circuit thereat, trunk and subscribers boards at a second central oflice, a trunk circuit joining said first central oflice and'said trunk board, a'transfer circuit connected to and extending saidtrunk circuit to said subscribers board, a signal for said transfer circuit at said subscribers board, a control relay'for said signal responsive to the connection of said'link circuit with said trunk circuit to operate said signal, a link circuit at said subscribers board, a relay associated with said transfer circuit and responsive to the connection of saidsecond link therewith to render said signal inoperative, a subscribers line connected to the free end'of each of said link circuits, supervisory signals for said first link circuit operated upon restoration of the receivers at the connected substations to furnish disconnect signals at saidfirst central oflice, and supervisory signals associated with said seconl link circuit and controlled by said control relay of said transfer circuit, said control relay being deenergized in response to the disconnection of said first link circuit from said trunk circuit to cause the operation of said supervisory signals of said second link circuit to furnish disconnect signals to the operator at said subscribers board.

In witness whereof, I hereunto subscribe my name this 9th day of March, A. D. 1915.

LEWIS H. JOHNSON.

Witnesses r E. EDLER,

K. L; STAHL.

uoplesof this patent may beobtained for five cents eaeh,-by 'addressingthe .Gommissioner of latents, Washington, D. 0. 

